Field of Invention
The present invention relates to a bolt that can secure conductivity with the nut even when fastened to a nut to which coating is applied.
Description of Related Art
In the production lines for automobiles and the like, bolts are used to attach various parts to a body to which coating treatment is applied. Especially in the case of attachment of a part which must secure conductivity with the body, a special bolt called an earth bolt is used. This bolt includes a coating peeling part which peels coating adhered onto the inner circumferential surface of a nut, and functions to peel coating for establishing metal touch between the bolt and the nut, thereby securing conductivity.
For example, Patent Literature 1 discloses an earth bolt designed in such a manner that a flank on the pressure side of a screw thread of the bolt is bent in the middle to dig the screw thread into a female screw, thereby bringing the screw threads into contact with each other. Also, Patent Literature 2 discloses an earth bolt in which a convex part having a flank angle which is approximately equal to the flank angle of a female screw is formed in a flank on the pressure side of a screw thread.
However, the bolt of Patent Literature 1 is intended to peel coating only by a tip end part of the screw thread, and thus coating cannot completely be peeled. Even if coating can be peeled, the peeled coating invades into a gap between the screw threads, thereby disadvantageously causing a conduction failure. Also, the bolt of Patent Literature 2 is intended to be fastened by digging the convex part formed in the flank on the pressure side of the screw thread and having a flank angle which is approximately equal to the flank angle of the female screw, into the nut, and thus disadvantageously requires a high fastening torque in order to secure conductivity.